LAS VEGAS, NOV. 21 -- Mexico's unbeaten Julio Cesar Chavez battered champion Edwin Rosario with unrelenting flurries of punches tonight before stopping him in the 11th round to win the World Boxing Association lightweight title.

Rosario was bleeding heavily from several cuts when his corner threw in the towel and referee Richard Steele stopped the fight at 2:36 of the 11th round.

Rosario was never down in the fight but took a vicious beating at the hands of Chavez (55-0, 46 knockouts), who closed the champion's left eye in the 10th round and cut him in the mouth and over the right eye.

Chavez, the World Boxing Council's super featherweight champion, took command from the opening bell of the scheduled 12-round fight, much of which was fought in Rosario's corner, where he was pinned by his stronger and quicker opponent.

Chavez, fighting before a crowd of about 8,000 at the outdoor arena of the Las Vegas Hilton, used a devastating left hook to establish a strong inside attack that Rosario could not hold back. Chavez stunned Rosario on several occasions but was not able to put the Puerto Rican down in the fight.

In the sixth round, Chavez bloodied Rosario's nose with a flurry of punches and landed a big right hand that put the champion into the ropes. Rosario's mouth began bleeding in the eighth round and a cut appeared over his right eye in the ninth.

Chavez, sensing a knockout, went all out in the 10th round, giving Rosario (27-3) a beating in his corner that closed his left eye completely. The ring physician looked at the eye between rounds but let the fight continue.

In the 11th, Chavez came running out and backed Rosario into his corner again, hitting him with a right that knocked the champion's mouthpiece out. Chavez followed with a series of head punches and was hitting Rosario at will when the bout was stopped.

Chavez weighed 134 3/4 pounds while Rosario, who reportedly had to lose 13 pounds in the two weeks before the fight, came in at the lightweight limit of 135.H